Congrats, fine camera indeed. I would look for a really good 90mm, Grandagon, Super Angulon or Nikkor, as these work well as a "normal" lens for your 6x7 format and can be pressed into service as a good covering wide angle for 5x4.
Next would be a good 150 or 180 which will serve as your standard for 4x5 and a bit long on the 6x7. There are really good super wides, 56m 75mm, that will serve as wides on the 6x7 and also cover 5x4 if you are contemplating using the 6x7 back a lot.
I must admit that although I have a 6x7 and 6x9 Super Rollex back for my Linhof I rarely use them, preferring 5x4 or a 6x12 back.